Throttle surging while driving constant speed

[Lukeis]

Hi gurus

im currently on a lap of aus and have noticed this issue for the past two weeks.

trying to drive a constant highway speed but the revs keep surging despite being very constant on the accelerator or having cruise control on.

it’s quite annoying and happens with or without the caravan on the back. I can feel it slightly vibrate the car when the van is on before jumping back a gear. Without the van on you can hear it and slightly feel it but generally holds the same gear.

see video here
YouTube (https://youtu.be/oUZvSLtWW6s)
have had a gearbox service a year ago. Is there anything I can check on the road?? Currently in streak bay in SA and about to go up the middle of aus so it’s making me a little nervous


https://youtu.be/oUZvSLtWW6s

[discorevy]

looks like torque converter clutch slip

[Lukeis]

looks like torque converter clutch slip

thanks, what’s the fix for that?

[Lukeis]

Should I consider resetting the adaptive learnings?

[gotaflat]

could be gbox, but suspect you may have other symptoms.

Tried in sport mode? does that happen then?

I had something similar may be not that noticeable until the end (I was blaming cruise control) - after a while i got fault..ended up being a turbo (consequently 2). Hope not

[Eric SDV6SE]

#1 torque converter slip. Get fluid level checked, if possible have a look at the fluid itself,should be relatively clear, not blackened. Others on here have said a tube of Dr.Tranny does help. A new TC may be required.

#2 valve body seals leaking, allowing fluid to bypass, forcing the tc to keep up. How does the shift feel? Harsh, clunks? Does it flare (i.e. rev up instantly before or after the shift? This needs a valve body rebuild.

#3 vacuum system, leak in intake tract, but these typically fault quite quickly and the car drops into restricted performance mode. Could be failing throttle body o ring.

#4 turbo, unlikley IMHO as this will drop the car into RP instantly, no surging.

[Lukeis]

Tested sport mode as follows

driving at around 100km hr

flick to sport mode:
car kicks back a gear, revs increase from circa 1500rpm to 2100rpm
no surging

use command shift to shift up a gear:
car drops back to circa 1500rpm and does not seem to surge

this is odd because I would have expected command shift 6th gear to be the same as auto 6th gear.

any help with this info?

[Eric SDV6SE]

Sports mode ups the line pressure in the valve body and subsequently in the tc. So S6 is not exactly the same as D6 in terms of line pressure. Std for it to shift down a gear when moving from D to S. The extra pressure may be enough to override tc slip for a while. If it is the tc slipping, it will eventually require a rebuild.

Do you know when the last transmission fluid change was? A flush and new fluid may help

[Lukeis]

Gday Eric

thanks for that info, TC rebuild sounds expensive.

would I assume like a clutch the longer you push it the worse the slip?
Will letting the problem exist flow onto other issues or is it safe to keep going for a while? I’m not sure what help I could get in this area of SA

[Eric SDV6SE]

Hi Lukeis,

Yes, provided the surging IS the tc slipping, its kinda like a mechanical clutch. The vanes / scoops inside wear, allowing fluid to bypass and so the engine side spins faster or slower than the transmission side. The transmission can keep up for a bit, or compensate to some degree depending on how much wear. Like any coupling it wears, especially if the fluid is dirty.

Can last 100km or 10000km, hard to tell. From what youve said theres little or no shudder,so sounds like youve caught it early. Id be trying to get it to a nearby workshop for a good check over.

[discorevy]

thanks, what’s the fix for that?

2 tubes of Dr tranny should stop the shudder / deglaze the TCC temporarily, until you can get a flush / metal pan and filter conversion


Should I consider resetting the adaptive learnings?

Definitely not


Hi Lukeis,

Yes, provided the surging IS the tc slipping, its kinda like a mechanical clutch. The vanes / scoops inside wear, allowing fluid to bypass and so the engine side spins faster or slower than the transmission side. The transmission can keep up for a bit, or compensate to some degree depending on how much wear. Like any coupling it wears, especially if the fluid is dirty.

Can last 100km or 10000km, hard to tell. From what youve said theres little or no shudder,so sounds like youve caught it early. Id be trying to get it to a nearby workshop for a good check over.


It is basically an electronically controlled wet clutch that generally glazes to start with , no vanes involved.
what happens is the control unit commands the clutch to lock up ,clutch slips , backs off , unit commands engagement again , slips again etc. This happens very quickly ( the rumble strip scenario if very glazed and high load ) or slower ( rev fluctuation ) in higher gears

[josh.huber]

Can really only be a torque converter issue. Speed is constant. So you wouldn't assume engine related.

Apart from that a slipping clutch, not really heard of that often.

Probably find a tranny shop that can dump and flush your fluid and add dr tranny. Land Rover Spares in Mackay can put it in an airbag for you if you need it. Lots of info on new aftermarket fluids.

[Lukeis]

Thanks all, this is really helpful and seems fairly conclusive.

I had the gearbox flush and conversion 30,000km ago to the steel pan so it’s a shame it’s playing up already.

will have to cross my fingers and hope we make it to Alice springs and someone reasonable can help me there

[Lukeis]

So is a flush a temporary fix or a new TC more likely on the cards? Any idea of the costs for that?

[Bulletman]

Thanks all, this is really helpful and seems fairly conclusive.

I had the gearbox flush and conversion 30,000km ago to the steel pan so it’s a shame it’s playing up already.

will have to cross my fingers and hope we make it to Alice springs and someone reasonable can help me there

Suttons in Alice Springs are very good and know their stuff. They should be able to help when you get there.

If you only had the trans oil done 30k ago do you know if they did a full flush , or ,just drop the sump only.

maybe its low on fluid.

Bulletman

[Lukeis]

Suttons in Alice Springs are very good and know their stuff. They should be able to help when you get there.

If you only had the trans oil done 30k ago do you know if they did a full flush , or ,just drop the sump only.

maybe its low on fluid.

Bulletman


im not clear if they did a flush or just dropped the oil.

I do know they initially used the wrong oil and it went back a few days later for lifeguard 6 due to a vibration. From memory they also added dr tranny afterwards to help

it’s been brilliant since then and for the first two months of this trip with LOTS of towing.

I’ll give Sutton’s a bell when I get there in two weeks. Is there a way to check the oil level without a hoist?

[INter674]

Fault codes may give the answer which could be engine related and if g box may require a reflash to resolve.

I would not rule out an engine issue at this stage.

Is that fuel reading normal..seems a bit heavy even for towing?

[Lukeis]

That’s a good pick up, yep I’m usually running at 16L/100 for towing and was doing so for the whole trip but this also changed in the past two weeks and has soared up into the 18’s even up to 18.7

I figured this could be related to the issue above, or perhaps because I’ve been driving closer to 100km hr now that the roads are straighter whereas prior I was generally towing closer to 90kph

[INter674]

Jags albeit with the petrol V6 but same gearbox have had similar surging issues which were thought to be the TC but which turned out to be engine related eg dirty MAF. But yes some were TC related eg failed TC o ring. Shifting gears also changed the surging pattern prolly due to engine management...maybe dumping more fuel at higher revs/lower gears.

Diagnosis is prob the key to finding the cause.

[Lukeis]

158721
I’ve noticed a bit of oil wetness here, could this be related?

ive cleaned away today to see how quickly it returns

[coopers1969]

I too have something similar but only over 110km but my revs don’t do that they stay constant. Mine happens at cruise or myself controlling the speed. When cruise is set at 110 my speedo reads 111km then drops back to 110km and the speeds up to 111km so on and so forth, but doesn’t do it at cruise control set at 100 or below, even though the my speedo is reading 101 km. Very weird all fluids done trans. TC, diffs it is a 3 litre D4.

[Eric SDV6SE]

The cruise control goes up in 2kmh increments,prolly just a sensor calibration issue if that...within tolerance (just)

[DiscoJeffster]

Yeah Eric is spot on. It’ll move within 2kph either side of the set speed before it takes more severe action to maintain it

[coopers1969]

Yeah Eric is spot on. It’ll move within 2kph either side of the set speed before it takes more severe action to maintain it

Thanks for the info I just find it strange that you get a real surge to get that extra kilometre back, if cruise is set at 110 km electric speedo says 111km then it drops off back to 110 and surges to 111 again you can really feel it in the car my old D3 never did that just a bit strange.

[441]

I'm with Coopers1969. I have a 2011 D4 SDV6 and it's doing 'exactly' the same thing and has been doing it for the last few months. 108kph or less and ops normal. If I manually drive at 110kph or set cruise control to 110kph or higher it 'hunts' to maintain speed. It's not behaving as though it's just fluctuating around the set speed in a normal fashion. It really feels as though a fault somewhere is not allowing it to maintain a smooth, constant speed from above 108kph and it's definitely hunting and surging to maintain speed. Other occupants in the car can feel it and have asked if that's me driving poorly or the vehicle doing it. I too have had a complete transmission fluid flush and replacement with new filter and bottom pan by well regarded Ritters in Melbourne. It's just been in for an unrelated service and they did everything they could to identify the problem to no avail. No fault codes. If I'm towing, there's a light vibration felt throughout the vehicle at speeds above 104kph. Not sure if it's directly related to the above-mentioned issue or not but it began around the same time the speed 'hunting' issue began. Vibration only when towing. Different trailers makes no difference to vibration issue.

[Bungee]

Diagnosed by Range Rover Rockhampton. Oxygen Sensors.
im currently on a lap of aus and have noticed this issue for the past two weeks.

trying to drive a constant highway speed but the revs keep surging despite being very constant on the accelerator or having cruise control on.

it’s quite annoying and happens with or without the caravan on the back. I can feel it slightly vibrate the car when the van is on before jumping back a gear. Without the van on you can hear it and slightly feel it but generally holds the same gear.

see video here
YouTube (https://youtu.be/oUZvSLtWW6s)
have had a gearbox service a year ago. Is there anything I can check on the road?? Currently in streak bay in SA and about to go up the middle of aus so it’s making me a little nervous


https://youtu.be/oUZvSLtWW6s[/QUOTE]

[Wahgilad]

Lincoln Landrover 0886821927 have been around for a long time.
They have a good reputation...knowledge, helpfulness & skill.

About 2 hours South of Streaky Bay.

Towing to The Alice with your problem would not thrill me.

Hope you get it sorted

Don

[Ferret]

I have a 2011 D4 SDV6 and it's doing 'exactly' the same thing and has been doing it for the last few months. 108kph or less and ops normal. If I manually drive at 110kph or set cruise control to 110kph or higher it 'hunts' to maintain speed. It's not behaving as though it's just fluctuating around the set speed in a normal fashion. It really feels as though a fault somewhere is not allowing it to maintain a smooth, constant speed from above 108kph and it's definitely hunting and surging to maintain speed. Other occupants in the car can feel it and have asked if that's me driving poorly or the vehicle doing it. I too have had a complete transmission fluid flush and replacement with new filter and bottom pan by well regarded Ritters in Melbourne. It's just been in for an unrelated service and they did everything they could to identify the problem to no avail. No fault codes. If I'm towing, there's a light vibration felt throughout the vehicle at speeds above 104kph. Not sure if it's directly related to the above-mentioned issue or not but it began around the same time the speed 'hunting' issue began. Vibration only when towing. Different trailers makes no difference to vibration issue.

Remove your throttle body and give the throttle position sensor a good clean out from the inside. It may be gummed up and not be moving freely. This is especially true if you have not had the secondary turbo drain mod fitted.

If it is sticky it will cause surging as you describe but does not throw fault codes. Try it.

[Eric SDV6SE]

Just be gentle with the throttle butterfly, last you want is to damage the servo motor.

[coopers1969]

I'm with Coopers1969. I have a 2011 D4 SDV6 and it's doing 'exactly' the same thing and has been doing it for the last few months. 108kph or less and ops normal. If I manually drive at 110kph or set cruise control to 110kph or higher it 'hunts' to maintain speed. It's not behaving as though it's just fluctuating around the set speed in a normal fashion. It really feels as though a fault somewhere is not allowing it to maintain a smooth, constant speed from above 108kph and it's definitely hunting and surging to maintain speed. Other occupants in the car can feel it and have asked if that's me driving poorly or the vehicle doing it. I too have had a complete transmission fluid flush and replacement with new filter and bottom pan by well regarded Ritters in Melbourne. It's just been in for an unrelated service and they did everything they could to identify the problem to no avail. No fault codes. If I'm towing, there's a light vibration felt throughout the vehicle at speeds above 104kph. Not sure if it's directly related to the above-mentioned issue or not but it began around the same time the speed 'hunting' issue began. Vibration only when towing. Different trailers makes no difference to vibration issue.

If you find out what is causing it keep me in mind my local also couldn’t find any issues.

[441]

Remove your throttle body and give the throttle position sensor a good clean out from the inside. It may be gummed up and not be moving freely. This is especially true if you have not had the secondary turbo drain mod fitted.

If it is sticky it will cause surging as you describe but does not throw fault codes. Try it.

Thanks Ferret. I have had the secondary drain mod fitted.

[Lukeis]

Just to close this one out.

the final fix was a full gearbox rebuild - in DArwin, but through AB in Victoria. Total cost $7860

Yes that hurt.

[INter674]

Just to close this one out.

the final fix was a full gearbox rebuild - in DArwin, but through AB in Victoria. Total cost $7860

Yes that hurt.

Argh...that's beepin expensive..but necessary I guess🤤

[DiscoJeffster]

Just to close this one out.

the final fix was a full gearbox rebuild - in DArwin, but through AB in Victoria. Total cost $7860

Yes that hurt.

Jesus mate. Have you entirely rebuilt the car top to bottom while up there?

[Lukeis]

Prettt much, The list of things I’ve done in the last four months is very large - it’s going to be a brand new car soon, was going to sell it for a new one but may not have to now!!